Electronic devices respectively electronic components such as micro-electromechanical system (MEMS) devices are of increasing importance. Many type of systems use sensors to detect the value of a property of a physical system and to generate a corresponding electrical signal representing the sensed value.
Accelerometer sensors for example comprise a mechanically active component, e.g. an acceleration dependant oscillating mass and rely on electromechanical sensors, which translate particular types of acceleration, such as rotational or linear acceleration, into corresponding electrical signals.
Since such electronic devices are quite sensitive, they need to be protected by assembling them in some kind of package. For the manufacturing of electronic or other devices for micro systems many technologies have been developed, which enable precise forming of structured encapsulation or passivation layers and/or cavities.
Typical packaging or housing concepts, as for example moulding in plastics, are disadvantageous because the mechanical properties of said sensitive components are disturbed or even damaged. In case of SAW-filter-devices for instance even the material on the surface influences the characteristics of said filter devices.
To avoid such disturbance and to protect such sensitive electronic device, wafers with corresponding sensitive electronic devices are bonded with a second wafer or a lid wafer. Said second wafer comprises holes or trenches in the area or at the position of said electronic devices. These holes or trenches of said second wafer are fabricated in such a way that they form a cavity above the sensitive structures after bonding said second wafer to said first wafer.
DE 101 47 648 A1 for example discloses this concept for the fabrication of pocket-shaped structures for a glass lid used for packaging MEMS devices.
Alternatively also expensive ceramic packages are used to protect sensitive components.
DE 102 06 919 A1 discloses a method for packaging electronic devices using a process with the following steps: Putting said electronic devices on a first wafer, fabricating a frame structure around each electronic device and covering said frame structure with a lid structure placed on a victim layer. The frame structure around each electronic device and the covering form a cavity housing and protecting the electronic device. As already mentioned above, many types of systems use electronic devices such as sensors to detect the value of a property of a physical system and to generate a corresponding electrical signal representing the sensed value. These electrical signals are commonly provided to electrical integrated circuits, located off-chip or in adjacent locations on-chip, in order to enable a desired function, e.g. amplification, discrimination and/or signal conversion, to be performed.
In the case of a separate packaging of electronic device and associated driver and/or controller integrated circuit, the packaged electronic device is mounted on a printed circuit board along with the driver and/or controller integrated circuit, which is packaged in a similar manner. Collectively they perform the desired function, e.g. a sensing function.
Since the packaging of the electronic device and the packaging of the integrated circuit are generally significantly larger than the corresponding electronic device respectively the integrated circuit, the packaging contributes notably to the dimensions and also to the costs of the assembly on the printed circuit board.
Further, the mounting of the electronic device in the packaging limits, how close the electronic device can be placed with respect to the integrated circuit performing the controller and/or driver function. This can in turn unnecessarily limit the electrical performance of the electronic system or increase the susceptibility to noise.
WO 01/29529 A2 discloses a packaging of micro-mechanical sensors and associated control circuits. The micro-mechanical sensor is fabricated on a semiconductor wafer and the control circuit on a another semiconductor. A cavity is etched on the back side of the control circuit wafer, the cavity being formed such that the sensor on the other wafer fits within the cavity when the wafers are brought together in an adjoining relation.
Document U.S. 2004/0173913 A1 describes a capacitive semiconductor, a sensor chip and a circuit chip being contained in a package. Said sensor chip in mounted onto said circuit chip to provide a stack structure. Said stack structure is contained in said package. Said package is made of single ceramic substrates which are inner-hollowed. Said circuit chip is positioned onto the top side of a plate.
U.S. Pat. No. 5,701,033 relates to a semiconductor device comprising a substrate having a hollow cavity for mounting a semiconductor element therein and a lowered step surface at a periphery of the cavity for mounting a chip component thereon. Said semiconductor element is mounted within the cavity and said chip component embodied as a chip capacitor is mounted to the lowered step surface.
Document JP 2002171150 describes the structure of a package for piezoelectric vibrating devices having one side which is positioned on the top side of a carrier by means of a type of “pedestal”.
U.S. 2004/0077117 A1 relates to a feedthrough design and a method for a hermetically sealed microdevice. Among other things a glass wafer and a silicon wafer are assembled to an assembly wafer which is diced into single microdevices.
Therefore, it is the object of the present invention to provide an easy, size and cost reduced but safe concept to package or house electronic devices or electronic devices together with their associated driver and/or controller integrated circuits, in particular by using conventional integrated circuit fabrication techniques and conventional packaging technologies.